The question continues to perplex scientists who enjoy perplexing questions: How did birds learn to fly? For 150 years, since Darwin published, scientists have known that modern birds evolved from dinosaurs and that wings and flight had to evolve from that starting point. The fossil evidence indicates that, for a long time, bird ancestors had little stubby appendages instead of wings. These proto-wings were too small to get the animal off the ground or keep it in the air for long.
Two schools of thought developed. Ornithologists developed the idea that early bird ancestors climbed up trees or slopes and then glided to the ground a distance away. This adaptation helped the early proto-birds escape predators, so they survived and their wings lengthened and eventually they could fly, which was an even greater evolutionary advantage than gliding. (If you want a long name for the scientists who think this, call them “arborealists.”)
Another school of thought, usually attended by paleontologists,— call them “cursorialists” — believe that the fossil similarities between birds and dinosaurs require that bird ancestors ran along the ground, beating their little feathered stumps, got airborne for a short distance and then kept running and flapping until they escaped a predator and until, generations later, they were all flying. For perspective, remember that the oldest bird fossil so far, Archaeopteryx, a flying reptile is from the late Jurassic, 150 million years ago although it probably began its journey to flight at least 100 million years before that. (Almost all birds were flying by 55 million years ago and modern bird families were well established by 35 million years ago; thirty-four million seven hundred thousand years before the first Homo Sapien arrived on the planet.)
Now comes news that both the “ground-up” and the “tree down” theorists were right. And wrong. Maybe. The proto-wings on those earliest bird ancestors may have actually helped the early birds stay on the ground.
A scientist at the University of Montana, using high speed cameras, has made an interesting discovery: Birds do not vary the angle of their wings nearly as much as once thought. In fact, no matter what the bird is doing; diving, climbing, turning, landing, taking off, the angle of its wings doesn’t change much. It is also an angle that helps keep some birds on the ground as they run up inclines. Acting like spoilers on a race car, the proto-wings kept some birds from lifting off inclined surfaces. Using that downward air flow in combination with their feet, the theory goes, the early dinosaur-birds were able to run up steep surfaces faster than their predators and then glide to the ground off a cliff or tree for a soft landing. The predators, even if they could follow the bird up the steep slope, couldn’t follow it off the cliff without crashing to the earth far below.
That is exactly how many baby Galliformes (chickens, quail, chukas, partridges, turkeys) learn how to fly. Able to run at birth, they don’t learn to fly until later. In the meantime their developing wings keep them on the ground where they can run. Which, if you can’t fly yet, is the next best way to get away from predators. Watch a baby chick run and you may be time-traveling back to the Triassic, two hundred fifty million years ago.
For more on the work of Dr. Ken Dial of the University of Montana who did the work with the high speed cameras, here is the story on Science Daily which formed the basis for this post.
(University of Montana (2009, March 3). How A New Theory Of Bird Evolution Came About. ScienceDaily. Retrieved March 7, 2009, from http://www.sciencedaily.com- /releases)